/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.commons.lang3;

/**
 * <p>Operations on {@link CharSequence} that are
 * {@code null} safe.</p>
 *
 * @version $Id: CharSequenceUtils.java 1606051 2014-06-27 12:22:17Z ggregory $
 * @see CharSequence
 * @since 3.0
 */
public class CharSequenceUtils {

	private static final int NOT_FOUND = -1;

	/**
	 * <p>{@code CharSequenceUtils} instances should NOT be constructed in
	 * standard programming. </p>
	 * <p>
	 * <p>This constructor is public to permit tools that require a JavaBean
	 * instance to operate.</p>
	 */
	public CharSequenceUtils() {
		super();
	}

	//-----------------------------------------------------------------------

	/**
	 * <p>Returns a new {@code CharSequence} that is a subsequence of this
	 * sequence starting with the {@code char} value at the specified index.</p>
	 * <p>
	 * <p>This provides the {@code CharSequence} equivalent to {@link String#substring(int)}.
	 * The length (in {@code char}) of the returned sequence is {@code length() - start},
	 * so if {@code start == end} then an empty sequence is returned.</p>
	 *
	 * @param cs    the specified subsequence, null returns null
	 * @param start the start index, inclusive, valid
	 * @return a new subsequence, may be null
	 * @throws IndexOutOfBoundsException if {@code start} is negative or if
	 *                                   {@code start} is greater than {@code length()}
	 */
	public static CharSequence subSequence(final CharSequence cs, final int start) {
		return cs == null ? null : cs.subSequence(start, cs.length());
	}

	//-----------------------------------------------------------------------

	/**
	 * <p>Finds the first index in the {@code CharSequence} that matches the
	 * specified character.</p>
	 *
	 * @param cs         the {@code CharSequence} to be processed, not null
	 * @param searchChar the char to be searched for
	 * @param start      the start index, negative starts at the string start
	 * @return the index where the search char was found, -1 if not found
	 */
	static int indexOf(final CharSequence cs, final int searchChar, int start) {
		if (cs instanceof String) {
			return ((String) cs).indexOf(searchChar, start);
		}
		final int sz = cs.length();
		if (start < 0) {
			start = 0;
		}
		for (int i = start; i < sz; i++) {
			if (cs.charAt(i) == searchChar) {
				return i;
			}
		}
		return NOT_FOUND;
	}

	/**
	 * Used by the indexOf(CharSequence methods) as a green implementation of indexOf.
	 *
	 * @param cs         the {@code CharSequence} to be processed
	 * @param searchChar the {@code CharSequence} to be searched for
	 * @param start      the start index
	 * @return the index where the search sequence was found
	 */
	static int indexOf(final CharSequence cs, final CharSequence searchChar, final int start) {
		return cs.toString().indexOf(searchChar.toString(), start);
//        if (cs instanceof String && searchChar instanceof String) {
//            // TODO: Do we assume searchChar is usually relatively small;
//            //       If so then calling toString() on it is better than reverting to
//            //       the green implementation in the else block
//            return ((String) cs).indexOf((String) searchChar, start);
//        } else {
//            // TODO: Implement rather than convert to String
//            return cs.toString().indexOf(searchChar.toString(), start);
//        }
	}

	/**
	 * <p>Finds the last index in the {@code CharSequence} that matches the
	 * specified character.</p>
	 *
	 * @param cs         the {@code CharSequence} to be processed
	 * @param searchChar the char to be searched for
	 * @param start      the start index, negative returns -1, beyond length starts at end
	 * @return the index where the search char was found, -1 if not found
	 */
	static int lastIndexOf(final CharSequence cs, final int searchChar, int start) {
		if (cs instanceof String) {
			return ((String) cs).lastIndexOf(searchChar, start);
		}
		final int sz = cs.length();
		if (start < 0) {
			return NOT_FOUND;
		}
		if (start >= sz) {
			start = sz - 1;
		}
		for (int i = start; i >= 0; --i) {
			if (cs.charAt(i) == searchChar) {
				return i;
			}
		}
		return NOT_FOUND;
	}

	/**
	 * Used by the lastIndexOf(CharSequence methods) as a green implementation of lastIndexOf
	 *
	 * @param cs         the {@code CharSequence} to be processed
	 * @param searchChar the {@code CharSequence} to be searched for
	 * @param start      the start index
	 * @return the index where the search sequence was found
	 */
	static int lastIndexOf(final CharSequence cs, final CharSequence searchChar, final int start) {
		return cs.toString().lastIndexOf(searchChar.toString(), start);
//        if (cs instanceof String && searchChar instanceof String) {
//            // TODO: Do we assume searchChar is usually relatively small;
//            //       If so then calling toString() on it is better than reverting to
//            //       the green implementation in the else block
//            return ((String) cs).lastIndexOf((String) searchChar, start);
//        } else {
//            // TODO: Implement rather than convert to String
//            return cs.toString().lastIndexOf(searchChar.toString(), start);
//        }
	}

	/**
	 * Green implementation of toCharArray.
	 *
	 * @param cs the {@code CharSequence} to be processed
	 * @return the resulting char array
	 */
	static char[] toCharArray(final CharSequence cs) {
		if (cs instanceof String) {
			return ((String) cs).toCharArray();
		}
		final int sz = cs.length();
		final char[] array = new char[cs.length()];
		for (int i = 0; i < sz; i++) {
			array[i] = cs.charAt(i);
		}
		return array;
	}

	/**
	 * Green implementation of regionMatches.
	 *
	 * @param cs         the {@code CharSequence} to be processed
	 * @param ignoreCase whether or not to be case insensitive
	 * @param thisStart  the index to start on the {@code cs} CharSequence
	 * @param substring  the {@code CharSequence} to be looked for
	 * @param start      the index to start on the {@code substring} CharSequence
	 * @param length     character length of the region
	 * @return whether the region matched
	 */
	static boolean regionMatches(final CharSequence cs, final boolean ignoreCase, final int thisStart,
								 final CharSequence substring, final int start, final int length) {
		if (cs instanceof String && substring instanceof String) {
			return ((String) cs).regionMatches(ignoreCase, thisStart, (String) substring, start, length);
		}
		int index1 = thisStart;
		int index2 = start;
		int tmpLen = length;

		while (tmpLen-- > 0) {
			final char c1 = cs.charAt(index1++);
			final char c2 = substring.charAt(index2++);

			if (c1 == c2) {
				continue;
			}

			if (!ignoreCase) {
				return false;
			}

			// The same check as in String.regionMatches():
			if (Character.toUpperCase(c1) != Character.toUpperCase(c2)
					&& Character.toLowerCase(c1) != Character.toLowerCase(c2)) {
				return false;
			}
		}

		return true;
	}
}
